The present invention relates in general to performing distance measurement to target points, surfaces mapping by a minimum number of points for surface definition and positioning of target points by wireless means using a portable coordinate system and a PC. It is also related to automatic generation of as-built drawings, to marking positions in relation to an existing computer drawing, construction quality control, three dimensional virtual modeling, object location and the like.
Prior art for performing wireless measurements is based on laser-optical or laser scanning devices. The laser scanning devices perform vertical and horizontal scanning on a tight grid in order to determine the three dimensional positions of surfaces in their immediate surroundings. U.S. Pat. No. 6,781,683, for instance, discloses such a device. The patent describes a method for operating a laser scanning system. The laser scanning system can be used in construction projects to generate a field survey which may later be used by an architect or engineer to create construction drawings. In addition, relevant points from the construction drawings can be identified at the construction site with the scanning system. The main drawback of such systems is that they must rely on existing drawings and may not generate computerized three-dimensional drawings of the scanned objects and surroundings.
U.S. Pat. No. 6,246,468 overcomes this shortcoming. It is an integrated system which generates a model of three-dimensional objects. A scanning laser device scans the three-dimensional objects and generates a point cloud whereas each point indicates a location of a corresponding point on a surface of the objects. According to this point cloud a model is generated representing constituent geometric shapes of the objects. A data file is than generated, responsive to that model, which can be inputted to a computerized design system.
Although this system can produce computerized three-dimensional drawings of the scanned objects, it still has several limitations. Since laser based systems may only scan objects in their line of sight any interfering obstacle between the scanning device and the measured surfaces prevent them from achieving correct measurements. In addition, this is a highly complex system, which demands extensive computing resources.
It is therefore the purpose of the present invention to provide efficient and cost effective means for accurately performing wireless measurements in diverse environments, and which may automatically produce as-built three-dimensional computerized models and drawings (plans, sections and elevations).
It is yet another purpose of the present invention to provide wireless positioning means. Known in the art are several means for finding the location of an item or a person relying on radio frequency (RF) communication using RF identification (RFID) tags. Such systems are used in warehouses for keeping track of inventory and in large facilities for locating equipment and staff. Usually these systems determine the approximate position of a tag or may give indication as for the existence of a tag in an enclosed space, such as a room. In addition, most often these systems calculate the position of an object based on information about its previous location.
While these systems may provide a sufficient level of precision for their purposes, there is sometimes a need for a means which can determine the position of an item with greater precision. U.S. patent application no. 20040203846 provides such a solution. One embodiment of this patent application includes a collection of wall-mounted antennas. The item's location is calculated by gathering the phase difference or other timing information of signal generated by the signal transmitting device on the entity. This location information is then given to end user applications.
Although this patent application provides a solution for accurately determining the position of an item in a given enclosed space, such as a room, it relies on positioning the signal gathering devices on three different walls in that room. This system lacks the flexibility and portability sometime needed. There is therefore a need for a means for calculating the precise location of an item without relying on previous information. In addition the means should have sufficient flexibility so it may provide these capabilities while being able to operate in different surroundings and environments.